Plant biomass of grasses in active restoration grasslands shows stronger association with its eco-physiological properties than native grasslands alongside degradation

Grassland degradation can affect plant eco-physiological properties and thus influence ecosystem productivity and ecosystem function. However, how land degradation affects the relationship between plant biomass and eco-physiological properties of active restoration grasslands and native grasslands in alpine meadow is less understood. A series of degraded grasslands (non-degraded, slightly degraded, moderately degraded, heavily degraded and extremely degraded grasslands) and a series of active restoration grasslands (active restored grasslands with different growth time, 5 years, 9 years, 11 years, 14 years and 17 years) were selected to investigate the relationship between eco-physiological properties and aboveground biomass (AGB) of grasses alongside degradation. Results showed that the AGB, net photosynthetic rate (Pn) and plant nitrogen (N) concentration decreased significantly with increased levels of degradation in native grasslands. Plant photosynthetic capacity, plant N and phosphorus (P) concentration significantly decreased at 9th year or longer than 9 years of replanting time in active restoration grasslands. Plant eco-physiological properties in active restoration grasslands shows stronger association with its AGB than native grasslands. In native grasslands, degradation affect AGB directly and through Pn indirectly. In active restoration grasslands, degradation affect AGB directly and through Pn, plant N and P indirectly. Our results indicated that through improving plant nutrients to restore degraded active grasslands may be more effective than to restore degraded native grasslands.